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Thread: SM420 install tip

  1. #1
    Join Date
    Oct 2009
    Location
    Atchison, Kansas
    Posts
    94

    Default SM420 install tip

    If you noticed my other post you'll know that I am finishing up a conversion on my CJ3A. I installed a Dauntless and an SM420.
    I thought I would share one of my misfortunes with you so that it may prevent someone the headaches I have suffered
    When I first got my motor/clutch/tranny in I realized that the clutch would not disengage. After trying 2 clutches, 5 different length throw out bearings and a number of other remedies I solved the problem. (I actually pulled the motor 10 times!!!!)
    The problem turned out to be that the tranny input shaft splines were about 3/16 too short and this was binding my clutch disk into my flywheel.
    I took a die grinder and extended the splines and all is well now.

    hope this prevents someone from having the same problems.

    Curtis
    1950 CJ3A , Dauntless Saginaw PS, SM420 D44 w/ Detroit locker Warn FF ,D25 w/lockright,3" lift springs, 33" mud terrains, daily driver
    1949 CJ2a project 4sale

    God, family, country ....... IN THAT ORDER!!

  2. #2
    Join Date
    Sep 2007
    Location
    Eastern Washington
    Posts
    191

    Default Re: SM420 install tip

    Thanks for the heads up. I'm putting a SM420 and 225 in my CJ5. I'll keep that in mind.

  3. #3
    Join Date
    Oct 2009
    Location
    Atchison, Kansas
    Posts
    94

    Default Re: SM420 install tip

    Not sure if all of the SM 420 trannys have this type of shaft but mine sure did.

    My tranny is the early type without the front seal.

    PS: The napa diaphram clutch kit works perfectly (throwout bearing and all) with this application.
    1950 CJ3A , Dauntless Saginaw PS, SM420 D44 w/ Detroit locker Warn FF ,D25 w/lockright,3" lift springs, 33" mud terrains, daily driver
    1949 CJ2a project 4sale

    God, family, country ....... IN THAT ORDER!!

  4. #4
    Join Date
    Sep 2007
    Location
    Eastern Washington
    Posts
    191

    Default Re: SM420 install tip

    Great info, thanks. Mine is a late military model. Probably 1970's or 1980's. So far it is just like the 1967 version that I can tell.

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